如何创建UIScrollView？

import UIKit

let scrollView = UIScrollView(frame: CGRect(x: 0, y: 0, width: 200, height: 200))

scrollView.contentSize = CGSize(width: 400, height: 400)

let contentView = UIView(frame: CGRect(x: 0, y: 0, width: 400, height: 400))
scrollView.addSubview(contentView)

scrollView.showsVerticalScrollIndicator = true
scrollView.showsHorizontalScrollIndicator = true
scrollView.scrollsToTop = true

let label = UILabel(frame: CGRect(x: 0, y: 0, width: 200, height: 50))
label.text = "Hello, World!"
contentView.addSubview(label)

view.addSubview(scrollView)